Motor driven damper blades per se are known in the prior art. Conventional systems of this type, however, have a number of deficiencies.
Prior art arrangements commonly employ a direct interconnection between the output shaft of the motor and the damper blade. Energization of the motor causes rotation of the output shaft and corresponding movement of the damper blade to a desired position (usually a closed position) relative to the conduit means with which the damper blade is operatively associated. Typically, the motor remains energized to hold the damper blade against one or more stops within the conduit which properly position the damper blade relative thereto. When the motor is de-energized, the prior art approaches often employ a spring in operative association with the damper blade to return the damper blade to its "normal" (usually open) position relative to the conduit. Again, a stop arrangement of suitable character is conventionally incorporated in the conduit to be engaged by the damper blade to maintain the damper blade in its normal position until the motor is once again energized.
Employment of the aforedescribed spring return feature when there is a direct or positive interconnection between the motor and the damper blade causes difficulties. The spring return tends to overstress the motor when the blade hits the stop at normal position. It has been found that the motor will "bounce" back and forth due to the inertia developed in the motor by the spring return. While the motor and damper blade eventually come to rest, the "bounce" action, especially over a period of time and frequent occurrence, causes considerable and undue wear of the motor's transmission gears, drastically shortening the life of the motor.
Another problem arises even before prior art dampers of the foregoing type are installed and operational. Persons installing such systems often test their operation by manually moving the damper blade. Of course, when there is a direct or positive connection between the damper blade and its associated motor, the transmission gears of the motor will also be forced to move to accommodate such manual movement of the damper. This can, and often does, result in breakage of the gears or other motor components.
In addition to the foregoing deficiencies, many prior art motorized damper constructions lack structural integrity and strength. For example, many such devices, particularly the conduit components thereof, can be relatively easily bent or warped during shipping, handling and installation. This can prevent proper operation of the damper by virtue of the conduit wall being contacted by the movable damper blade during movement between its operating positions.